The present invention relates to a lower thread automatic supply device for use in a sewing machine which moves a bobbin case along a given passage to thereby replace a bobbin within a hook.
In a sewing machine which carries out a sewing operation using upper and lower threads, especially, in an industrial sewing machine which carries out a high-speed sewing operation, a bobbin with a lower thread wound therearound must be replaced frequently. Generally, when the lower thread is consumed, the operation of the sewing machine is stopped once and a bobbin case with a bobbin stored therein is taken out from a hook; and, after then, a series of operations are executed by hand; that is, a new lower thread is wound around the bobbin and the bobbin case storing therein the bobbin with the new lower thread wound therearound is mounted into the hook again, or a previously prepared bobbin with a lower thread wound therearound is stored into the bobbin case and the bobbin case is then mounted into the hook.
However, such manual winding operation of the lower thread around the bobbin as well as such bobbin case replacing operation are very inefficient, resulting in the lowered productivity. In view of this, in Unexamined Japanese Patent Application Publication No. Hie. 7-68071 (corresponding to U.S. Pat. No. 5,694,874), Unexamined Japanese Patent Publication Application No. Hei. 8-173671 (corresponding to U.S. Pat. No. 5,839,679) and the like, the present applicants propose a lower thread automatic supply device which is capable of carrying out automatically an operation to wind a lower thread around a bobbin as well as a bobbin case replacing operation.
In particular, a bobbin replacing device which is provided in the above-disclosed lower thread automatic supply device, as shown in FIGS. 9 and 10, includes bobbin case grip means which holds and releases a bobbin case 1 with a bobbin stored therein to thereby take out a bobbin case within a hook and mount the same again into the hook; and, in more particular, the bobbin replacing device is structured such that the present bobbin grip means can be moved by delivery means 2 along a given passage to thereby move the bobbin case 1 cyclically between a hook 15, a residual thread removing device 4, and a lower thread winding device 5.
And, when a bobbin replacement request is given, the bobbin case 1, which is disposed within the hook and on which the lower thread is consumed, is taken out from within the hook 15 by the bobbin case grip means and the thus taken-out bobbin case 1 is delivered to the residual thread removing device 4, where the thread left on the bobbin is removed completely. The bobbin case 1 storing a thus emptied bobbin therein is delivered to the lower thread winding device 5, where a new lower thread is wound around the empty bobbin. After then, the bobbin with the new lower thread wound therearound is mounted into the hook 15 together with the bobbin case 1.
The thus structured conventional lower thread automatic supply device is disposed just under the hook 15; and, in particular, the components of the conventional lower thread automatic supply device, that is, the residual thread removing device 4, the lower thread winding device 5, and the delivery means 2 of the bobbin replacing device are respectively arranged under the hook 15.
Also, the present conventional lower thread automatic supply device is structured in such a manner that it can be mounted onto and removed from a sewing machine main body; for example, the present conventional lower thread automatic supply device can be mounted onto and removed from a device support portion 7 disposed under a bed portion 6 on the sewing machine main body side and, when the present conventional lower thread automatic supply device is mounted, the above-mentioned components 2, 4 and 5 forming the present conventional lower thread automatic supply device are arranged such that they have their respective given position relations with respect to the position of the hook 15.
However, in the present conventional lower thread automatic supply device, since it is disposed under the hook 15 of the sewing machine, not only cloth dust dropping down from a feed dog or the like of the sewing machine and thread trim scraps produced in a thread trimming device of the sewing machine can drop down onto the delivery means 2 and various sensor portions and can be easily attached thereto, but also lubrication oil supplied to the hook 15 can drop down or fly around so that it can stick to the delivery means 2 and various sensor portions. Due to this, the above-mentioned cloth dust and thread trim scraps can accumulate thereon in the form of sludge, which can cause the device to malfunction.
Also, in this type of conventional lower thread automatic supply device, unless the position relation thereof with respect to the hook position of the sewing machine, especially, with respect to the axis of the hook is set properly, then the mounting and removal of the bobbin case by the bobbin case grip means cannot be carried out positively. For this reason, when installing the conventional lower thread automatic supply device, there are required troublesome adjusting the setting operations for securing position precision. Further, in the conventional lower thread automatic supply device, the mounting relation thereof varies according to the kinds (head portions) of the sewing machines, and separately structured devices must be prepared to cope with the different kinds of the sewing machines.
Still further, in the conventional lower thread automatic supply device, after it is mounted, in accordance with the kinds (head portions) of the sewing machines or in accordance with the dimensional tolerances and assembling tolerances of individual sewing machines, the movement control amount of the delivery means must be adjusted, which makes it necessary to carry out an operation in which the position data (adjusting parameters) thereof stored in a control board provided externally of the lower thread automatic supply device are replaced and stored again.